Prior art workers have devised many types of nail driving tools wherein a nail is driven into a workpiece by a driver shiftable between a retracted position and a nail driving position. The teachings of the present invention are applicable to any such tool utilizing strips or coils of nails arranged in a spaced side-by-side row and connected together by carrier or collating wires which are welded to each nail. The strip or coil of wire collated nails is fed from a magazine such that the forwardmost nail of the row is located under the driver which advances to break the forwardmost nail from the strip or coil and drive it into a workpiece. Prior art workers have devised tools wherein the driver is actuated by pneumatic means, electromechanical means including flywheels, internal combustion means and the like.
While not intended to be so limited, for purposes of an exemplary showing the present invention will be described in its application to a pneumatically actuated tool. A pneumatically actuated tool is chosen for this purpose primarily because such tools constitute those most frequently encountered in the art. Examples of such tools are taught in U.S. Pat. No. 4,669,648 and in co-pending application Ser. No. 07/113,597, filed Oct. 26, 1987 in the names of Jay M. Steeves and Eric H. Halbert and entitled RESTRICTIVE TRIGGER ACTUATED VALVE ARRANGEMENT FOR A FASTENER DRIVING TOOL.
The use of wire collated strips or coils of nails is generally characterized by a problem. As each nail of the strip or coil becomes the forwardmost nail thereof, and is driven into a workpiece by the tool driver, the collating wires are broken at or near the forwardmost nail being driven. This leaves forwardly extending wire segments on the next succeeding nail, the wire segments extending outwardly from its shank. When the next succeeding nail advances beneath the driver and becomes the forwardmost nail of the strip or coil, the wire segments of this nail will hopefully remain attached to the nail and will be driven into the workpiece along with the nail. However, should the wire segments fail to remain attached to the nail, the resulting loose wire segments can become flying debris, or they can be trapped under the head of the driven nail. Such trapped wire segments are known in the art as "flags". Flags can snag, corrode, and are unsightly.
It will be understood by one skilled in the art that the quality of the welds of the collating wires to the nails is critical. If the collating wires simply become detached from the forwardmost nail as it is driven into the workpiece, experience has shown that occasional "stringers" of collating wire will be formed which cause several types of operating difficulties, including large flags. If the welds between the collating wires and the nails are weak, even in the practice of the present invention the welds may not be strong enough to pull the wire segments down into the workpiece. It is also possible to overweld, so as to weaken the wire near the weld. The actual welding process does not constitute a part of the present invention, and the disclosure to follow presumes adequate welding.
Experience has shown that most loose wire segments, when the welds are good, are created when the wire segments are broken from the nail as the nail enters the workpiece. It has been found that if the wire segments point down toward the point of the nail, it is very likely that the segments will be broken off when they hit the workpiece, particularly if the downwardly extending wire segments are located very close to the nail shank.
The present invention is based upon the discovery that with improvements to the guide body and drive track of the tool, and to the nail feed mechanism, the formation of loose pieces of collating wire and flags can be reduced significantly. Means are provided to assure that the collating wire segments of the nail to be driven are bent upwardly along the nail shank. The nails are adequately spaced along the collating wires to assure that the wire segments are of sufficient length to properly cooperate with the means that bends them upwardly along the nail shank. The feed mechanism is modified to provide support for the wire segments, to properly direct the wire segments to assure their cooperation with the means that bends them upwardly, and to assure that the collating wires break at or near the forwardmost nail of the row or coil.
Another problem encountered in the use of wire collated nail strips or coils is encountered if the head of the forwardmost nail being driven strikes the wire segments from which it has just been separated. The head may sever a piece of the segment or nick it. If a portion of a wire segment is severed, the severed portion becomes a loose piece of wire and the remainder of the segment still attached to the next succeeding nail is too short to cooperate with the segment bending means of the present invention. If the head of the forwardmost driven nail nicks the segment still attached to the next succeeding nail, that segment may not have sufficient strength to undergo the upward bending, or the entrance of the segment into the workpiece, without breaking. As a consequence, the present invention contemplates modification of the feed mechanism to prevent the head of the forwardmost nail being driven from striking the wire segment from which it has just broken away.